Die casting and die injection casting are commonly used to make metal parts. A die casting apparatus usually includes a pair of die halves each formed with a void corresponding to a portion of the metal article to be cast. When the two die halves are brought together in proper alignment, each respective void cooperates to form a die cavity having a shape of a metal part to be cast. Molten metal fills the void and solidifies as it cools in the die. Once the metal is solid, then the die halves are parted. Ejection pins may be activated after the dies are opened in order to push the cast metal part out of the die cavity. In some cases, a die release agent is first sprayed onto the die to prevent sticking of the metal part to the surface of the die.
An insert of an article of the same or a different metal or alloy may be placed in the die prior to casting. This complicates the die casting process, but offers advantages in some cases. These inserts are placed in the die cavity prior to die casting so that they become encapsulated by molten metal and become an integral part of a die cast article. For example, an insert may be located in a high stress portion of an article to bolster the casting, along contact surfaces to prevent coining or wear of the article, or to provide special properties such as electrical or thermal expansion properties.